A feature or organic optoelectronic devices is either that electrical energy is converted into photons (organic light-emitting diodes, OLEDs, or light-emitting electrochemical cells, LEECs) or that the opposite process occurs (organic photovoltaics, OPVs). It is important here that these processes run as efficiently as possible. For the sector of OLEDs, therefore, it is necessary ideally to use materials having maximum photoluminescent quantum yield. Limited efficiencies in OLED materials can be improved by using efficient materials which exhibit thermally activated delayed fluorescence (TADF), since, in contrast to purely fluorescent materials, up to 100% of the excitons, rather than 25% of the excitons formed in an OLED, can be utilized. The triplet excitons formed can also in this case be converted into singlet excitons, a state from which photons can then be emitted. A precondition for such thermal repopulation is a low energetic distance between the lowest excited singlet level (S1) and triplet level (T1). This may be achieved, for example, through use of copper(I) complexes (in this regard see, for example: H. Yersin, U. Monkowius, T. Fischer, T. Hofbeck, WO 2010/149748 A1) or else by means of purely organic materials (in this regard see, for example: Q. Zhang et al., J. Am. Chem. Soc. 2012, 134, 14706, WO 2013161437 A1).
There is also a large demand for new materials, as for example for deep-blue TADF OLEDs. Existing blue TADF materials often exhibit high exciton lifetimes, which are bad for efficient and long-lived OLEDs. Besides the aforementioned properties of the materials, their availability is also relevant with regard to commercialization. This includes the availability of synthesis building blocks, and also the cost and convenience of the actual synthesis of the functional material, particularly including the purification of this material.